Connect triac outputs and drive independently?

I want to add remote control to my sprinklers.
The present control box will be set to disable its control of the sprinkler valves, but its triacs will still be connected to the valves.
I will be using triacs with opto-isolated gating to turn each solenoid valve on/off using the 24VAC in the present control box.

Can I connect each of my zone wires to the same zone screw terminals in my present control box without causing a problem?

In other words, can I connect the outputs of two triacs to the same valve when one triac is gated off and the other is gated on, without damaging anything?

It's the unknown that is causing caution here. We can't actually guess exactly how the device is built, so we try not to steer you into a mistake, and consider that as probably the best result we can hope for.

This is a couple of ways your machine might be configured.
These might not be all the possible ways.
The goal here is to try to think of all the possible ways and tell you something that won't make any of them smoke.